Macular Thickness and Mesopic Visual Acuity in Healthy Older Subjects

Purpose/Aim: Impaired mesopic visual acuity (VA) is a risk factor for incident early age-related macular degeneration (AMD) This study examines relationships between macular thickness measurements and photopic or mesopic VA in healthy eyes. Materials and Methods: In 38 young and 39 older healthy individuals, total, inner, and outer retinal layer (IRL and ORL) thicknesses were measured in the macula region through spectral-domain optical coherence tomography (SD-OCT). Measurements were made across three subfields centered at the fovea: central foveal, pericentral, and peripheral. Best-corrected distance high-contrast (HC) and low-contrast (LC) VA were measured using Bailey-Lovie logMAR letter charts under photopic and mesopic luminance conditions. In addition, the low luminance deficit in VA (LLD, difference between photopic and mesopic VA) was calculated. Relationships were examined through Spearman correlation in each age group and through multiple linear regressions across all eyes. Results: No significant correlations were detected between photopic VA (HC-VA and LC-VA) and macular thickness measurements in each age group. In mesopic conditions, age and pupil size were independent predictors of HC-VA (p = 0.001) and age and pericentral ORL thickness predictors of LC-VA (p = 0.001). Central foveal thickness emerged as the unique independent predictor of LLD (HC-VA, p = 0.013 and LC-VA, p = 0.005). Only in the older age group, was central foveal thicknesses correlated with LLD (HC-VA, r = + 0.45; p = 0.004 and LC-VA, r = + 0.33, p = 0.038). Conclusions: Greater macular thicknesses were related to worse mesopic VA and low luminance deficit in healthy subjects.